Process for the heated drawing and fixation of filaments



Oct. 7, 1969 H. SCHIPPERS 3,471,608

PROCESS FOR THE HEATED DRAWING AND FIXATI ON OF FILAMENTS Fil ed Aug. 8, 1967 I 2 Sheets-Sheet 1 INVENTOR: HEINZ SCHIPPERS ATT'YS Oct.7,1969 HSCHPPERS 3,471,608-

PROCESS FOR THE HEATED DRAWING AND FIXATION 0F FILAMENTS Filed Aug. 8, 1967 V 2 Sheets-Sheet 2 INDUCTIVE I ROLLS HEATING RESISTANCE -TO VACUUM H E ATI NG pump DRAW ROLLS |-0ucnv HEATING :SHRINKAGE ROLLS ENCLOSURE Q TAKE-UP ROLL INVENTOR. HEINZ SCHIPPERS ATT'YS United States Patent PROCESS FOR THE HEATED DRAWING AND FIXA'IION 0F FILAMENTS Heinz Schippers, Remscheid-Lennep, Germany, assignor to Barmag Barmer Maschinenfabrik Aktiengesellschaft, Wuppertal, Germany Filed Aug. 8, 1967, Ser. No. 659,185

Claims priority, application Germany, Aug. 9, 1966,

Int. 'Cl. B29c 17/02 U.S. Cl. 264290 3 Claims ABSTRACT OF THE DISCLOSURE Process of heating a synthetic polymer thread over a first set of draw rollers at the drawing temperature of the thread and then over a second set of draw rollers at the fixation temperature of the thread while maintaining the temperature of the thread at least as high as said drawing temperature but below the fixation temperature in a linear path of the thread free of contact with heated surfaces between the sets of rollers, preferably carrying the drawing and heating steps under a common vacuum. Suitable apparatus comprises the two sets of draw rollers, means to heat the thread in its linear path between said sets of rollers in an at least partially enclosed heating zone, a readily detachable housing means over said sets of rollers and said heating means, and a vacuum pump connected to said housing for its evacuation. The thread produced has highly uniform properties for textile applications.

The invention is concerned with a process and a device for the heat treatment of a thread of a filamentary synthetic thermoplastic polymer, e.g. as a monoor multifilament thread, yarn or similar fibrous structure. The thread is adapted to run over two spaced drawing cylinders which can be separately heated and rotated at different peripheral velocities so as to permit both drawing.

and fixation of the thread.

Many different processes and devices have become known for the drawing or stretching of threads of synthetic polymers, in some instances including a fixation of the drawn thread with a certain degree of shrinkage. It is of course possible to subject polymer threads such as the nylons or polyesters to either a hot draw or a cold draw, but the thread must be heated for fixation.

For example, German Patent No. 951,290 provides heated cylinders employed singly or in pairs as supply rollers and drawing rollers as well as relaxation rollers. In U.S. Patent No. 2,942,325, a heated supply roller and a heating galette are used in combination with an unheated more rapidly rotated drawing roller, arranged one after the other. Between the heating galette and the drawing roller, the thread is not heated. No fixation is intended with this arrangement. U.S. Patent No. 2,509,741 suggests still another procedure wherein the thread is heated by radiation or direct contact as it runs between unheated rollers or cylinders placed at a certain distance from each other. As taught by the patent, this arrangement requires considerable space since two heating devices separated by an unheated roller or cylinder are required.

Still another procedure is demonstrated in Example 5 of U.S. Patent No. 2,956,330, wherein the thread runs from an unheated supply cylinder over a heated drawing pin as well as a heating device and only then over an unheated drawing cylinder. Thereafter, the thread is fixed and shrunk in another relatively long or spacious heating zone. In addition to the relatively large space requirements of this arrangement, the repeated heating using a multiple of heating elements is uneconomical. Furthermore, the procedure tends to be damaging to the filament or fiber structure of the thread, as evidenced by a diminished tensile strength and an excessive extension (elongation at break).

In Example 4 of U.S. Patent No. 3,090,997, a similar two-stage drawing procedure is described. In this case, the thread runs from an unheated supply roller to a heated drawing pin, then to a first heated drawing cylinder and thereafter over a heating drum or cylinder as well as a heating tube to a second heated drawing cylinder. In this arrangement, the filaments of the thread are mechanically stressed when running over the drawing pin. Again, the thread is drawn in two separate stages so that damage to the fiber structure occurs, apparently due to the repeated heating, stretching and cooling of the filaments.

It is an object of the present invention to provide a process and apparatus for the heat treatment of synthetic polymer threads, particularly to achieve a drawing or stretching followed by fixation of the thread, whereby the disadvantages of prior procedures and devices can be avoided. Other objects and advantages of the invention will be more apparent upon consideration of the following detailed specification.

It has now been found in accordance with the invention that a substantial improvement can be achieved in the heat treatment of a thread of a filamentary synthetic thermoplastic polymer by carrying the thread in running contact over a first and second heated rotatable draw means which freely support the thread in a linear path therebetween, and applying heat to the thread in an at least partially enclosed heating zone over substantially the entire linear thread path between the two draw means such that the temperature of the thread is maintained at least at its drawing temperature but below its fixation temperature. By maintaining the first draw means at the drawing temperature and the second draw means at the fixation temperature, preferably employing a second stage of smaller diameter on the cylindrical element of the second draw means, the thread can be drawn and fixed while accommodating shrinkage of the thread. Each of the heated draw means and the intermediate heating means adapted to heat the thread free of direct contact with heated surfaces are desirably mounted within a common enclosure in the form of an easily disassembled box or housing, preferably connected to a vacuum pump in order to evacuate the housing during the drawing and fixation of the thread.

A particular embodiment of the invention is set forth in the following description taken in conjunction with the drawings wherein:

FIG. 1 is a perspective view of a portion of the device of the invention showing a suitable arrangement of the individual thread contacting elements and heating means on a mounting panel, certain segments or elements being omitted or partly broken away;

FIG. 2 is a corresponding perspective view of a cover or lid which fits over the elements shown in FIG. 1;

FIG. 3 is a top plan view illustrating a series of covers or lids as mounted or being assembled on a common supporting plate, the remaining elements for heat treatment of the thread being omitted for the sake of clarity;

FIGS. 4 and 5 are each cross-sectional views taken on lines 44 and 5-5, respectively, of the heating element of FIG. 1 in order to illustrate a variation in the structure of this element over its length so as to supply different amounts of heat to the thread; and

FIG. 6 is a schematic view of the overall apparatus used in combination for the heat treatment of a synthetic polymer thread in accordance with the invention.

The term thread is employed herein with reference to the usual filamentary or fiber-like structure of synthetic polymers, The invention is not limited to specific threads or specific polymers but is especially useful with the conventional undrawn or only partially drawn threads of high molecular weight linear fiber-forming polymers such as the nylons, e.g. polycaprolactam or polyhexamethylene adipamide, or the polyesters such as polyethylene terephthalate. It will also be understood that the specific drawing or stretching temperatures as well as the temperature of fixation depend upon the particular polymer, the initial physical properties of the individual filaments and the desired properties in the drawn thread. These temperatures can be easily regulated by one skilled in this art in order to achieve a hot draw followed by heated fixation and, if desired, a certain shrinkage of the thread. There are various constructions and arrangements of drawing or stretching means which generally require rotatable cylinders, rollers or the like having different diameters and/ or different peripheral velocities in running contact with the thread in order to apply the required tension or degree of draw. The device illustrated herein represents a particular preferred embodiment of such draw means without excluding obvious variations falling within the scope of the appended claims.

Referring now to this specific embodiment illustrated in the drawings, the thread is initially supplied to the drawing means and heat treatment according to the invention by the apparatus shown at the uper end of FIG. 1. A drive shaft 1 is motor driven at a regulated speed together with the drive cylinder 2 with pressure being exerted on thread by means of the second roler 4 rotatably mounted on supporting arm 3 which in turn is pivotally mounted on the supporting shaft 5.

On the inner side of the mounting plate 6, there are positioned a first drawing cylinder 7 with its separating pin 8 and, at a relatively short distance therefrom, e.g. to 80 cm., a second drawing cylinder 9 with its separating pin 10. In this typical combination of a draw cylinder and separating pin of relatively smaller diameter, the pin is generally canted toward the cylinder to permit several windings of thread to progressively travel outwardly over both elements, and this pin need not be heated but should usually be freely turning on its supporting axis or shaft. One or both of the drawing cylinders can be constructed in stages, either to provide variations in the heat applied and/or to vary the speed of thread travel thercover by means of coaxial cylindrical segments of different diameter. Also, the cylindrical surfaces can be grooved or adapted to provide frictional adherence to the thread as in conventional elements of this type.

Each of the cylinders 7 and 9 are mounted for rotation and driven at a predetermined circumferential velocity according to the stretch or draw imparted to the threaded, e.g. with increasing velocity from drawing cylinder 7 to drawing cylinder 9. Both of the drawing cylinders 7 and 9 are heated in any suitable manner, preferably by internal inductive heating although hot gases such as steam or other means of electrically heating the cylinders from their interior outwardly to the thread contacting circumference are also feasible.

In the specific embodiment illustrated herein, cylinder 7 is a single stage draw means. The cylinder 9, on the other hand, is constructed in two stages with the primary roller or cylindrical segment 12 providing a draw means in cooperation with the separating pin 10, while the coaxially extending cylindrical portion 13 in cooperation with a second freely turning separating pin 11 provides a means of accommodating shrinkage in the thread at the fixation temperature. If desired, the two cylindrical stages 12 and 13 can be heated at different temperatures and their peripheral velocities are different due to the difference in their diameters.

In addition, the mounting plate 6 carries a heating element 14 which in the drawing is an electrically heated metallic bar, plate or rail with two oppositely disposed strips or side walls 14a and 14b which lie adjacent to or along the path of the thread over substantially its entire length as freely supported between the two draw means, i.e. between pins 8 and 10. The heating rail 14 is simply an electric resistance element capable of being heated to any desired temperature by conventional control means (not shown), independently of the heat supplied to the drawing cylinders. The side walls or strips 14a and 14b of this heating element are placed in close proximity to the thread path but without making direct contact with the thread so as to maintain the thread within the essential temperature range of the invention during its travel from the first draw means to the second draw means.

In FIGS. 4 and 5, it will be recognized that the heating rail 14 can be constructed with a variable profile, i.e. a gradually decreasing cross-section from top to bottom such that in being heated the temperature gradually increases from top to bottom. Other heating means are also suitable, e.g. by using an electrically heated tube or pipe, preferably having a longitudinal slot for ease in the insertion of the thread. It is equally useful to employ other forms of heating and various heating devices, such as infared light, electrical induction heating or steam heating provided that the thread path between the draw means is sufiiciently closed to apply heat indirectly to the thread and maintain the temperature within the prescribed limits.

When using a heated rail 14 or similar grooved or slotted enclosure, the ends thereof are preferably located quite close to the turnable separating pins 8 and 10 in order to avoid any cooling of the thread. For purposes of illustration, portions of the rail have been cut away in FIG. 1 and the respective distances between the heated cylinders and the separating pins have been enlarged, The length of the rail may also be substantially greater than illustrated, although it is a particular advantage of the invention that both drawing means as well as the heating means therebetween can be mounted in a relatively small space. Thus, there is practically no heat loss from the thread as it is Wound around the pair of draw rolls represented by cylinder 7 and pin 8, conducted through the heating rail 14 and then wound around the two-stage pairs of rollers represented by draw rolls 12, 10 and shrinkage rolls 13, 11.

It is particularly desirable to mount the drawing and heating means of the invention within an almost airtight box, housing or similar enclosure as shown in detail in FIGS. 2 and 3. The housing is preferably metallic in construction but lined with a suitable insulating material to prevent excessive heat losses. The mounting panel 6 acts as one side of this housing and is adapted to receive a cover or lid 23 by means of slots 15 in which the brackcts 17 connected to the cover by hinges 16 slide back and forth. The panel 6 also contains another slot or opening 19 for the bolt 20 on the locking lever 21. This locking lever is turnably or pivotally mounted to the inwardly spaced side wall 18 of the insulated cover 23 by means of a pin or bolt 22. If the cover is to be removed, the lever 21 is lifted by means of knob 26 from its position of rest on a pin or stud 24 as shown in FIG. 3 so that the bolt 20 is disengaged from the slot 19. In the closed position, the cover 23 is held tightly to the mounting plate 6 by engaging the bolt 20 in slot 19, the weight of the knob 26 being sufiicient to prevent accidental lifting of the lever. The ears 25 of the brackets or hinged flanges 17 prevent the cover 23 from being completely detached or removed from the mounting panel 6. Other means of partially or completely removing the cover are equally suitable.

In order to permit observation of the apparatus during operation, two viewing windows 27 are provided on the outer wall. The thread is run through the cover by means of an inlet slot 29 and a corresponding outlet slot at the bottom of the cover (not shown). In addition, the enclosure is in gaseous connection with a vacuum pump by means of a flexible conduit or hose 28 in order to evacuate air, steam or other gases from the interior of the enclosure. This evacuation is desirable not only to prevent an accumulation of undesirable gases but also to prevent an overheating of the enclosed apparatus. and structural members, thereby permitting a more careful control of the individually heated drawing cylinders and heating rail.

The overall operation of the apparatus can be explained with reference to the schematic sequence shown in FIG. 6, referring to the other figures of the drawing where necessary.

The thread 30 is withdrawn from a bobbin 31 and fed by means of the supply rolls 2 and 4 into the enclosure 23 through slots 29. The thread is first wound several times around the draw rolls 7 and 8 and is heated to its drawing temperature by the heated roll 7. The thread then runs in a linear path free of contact with other surfaces to the second set of draw rolls and 12. The heated roll or cylinder 12 is operated at a higher peripheral velocity than cylinder 7 so that the thread is primarily drawn or stretched between these two cylinders. The drawing point is usually reached as the thread unwinds or runs off from the separating pin 8. However, even after this point of drawing, the thread ordinarily still possesses a small percentage of its draw or stretch capacity.

Between the separating pins 8 and 10, the thread runs through the heating zone provided by the heating device 14 without coming in direct contact with the heated surfaces. In this heating zone between the two pins, the thread must be maintained at least at the drawing temperature, and it is preferable to gradually increase its temperature up to but in no case above its fixation temperature (e.g. up to about 80 C. above the drawing temperature in certain instances). The exact fixation temperature is maintained on the cylinder 9.

If shrinkage of the thread is desired as well as fixation, the thread is led over the first stage of cylinder 9 represented by rollers 12 and 10 and is then passed to the second stage represented by rollers 13 and 11. When driven on the same shaft, the roller or cylindrical segment 13 has a slower peripheral velocity than segment 12 because of its correspondingly smaller diameter, thereby permitting the thread to shrink. It is desirable, of course, to wind the thread several times around the stage cylinders 12 and 13 as well as their respectively coacting separating pins 10 and 11 so that these pairs of rollers can exert the forces required for drawing and shrinkage during the travel of the thread through the apparatus. The drawn and fixed thread then exits through the bottom of the enclosure and is collected on a suitable take-up spool or bobbin 32.

The box or enclosing cover 23 prevents substantial heat losses from the heated drawing cylinders and any heating means employed to maintain the freely supported thread at a temperature between the drawing and fixation temperatures, thereby providing a better use of the generated heat energy and a more economical process.

It is essential for purposes of the present invention to avoid any substantial cooling between the two sets of draw rolls, and for this reason, the heating rail or any other heating device should supply heat to the thread over practically the entire length of thread extending between the draw means. Of course, since the thread runs at a more or less rapid linear speed, it will tend to retain a certain amount of heat for short distances, especially if the enclosure has been evacuated. Certain minor adjustments in the position and arrangement of the various enclosed drawing, heating and fixing elements can thus be made without departing from the spirit or scope of the invention. Likewise, there is no absolute temperature required for any particular drawing, heating or fixing operation, nor is it essential to produce a shrinkage of the thread. Thus heating of the drawing cylinders may be accomplished in segments or stages merely if this is desirable in terms of the particular thread properties to be achieved. Naturally, the linear speed of the thread must be reduced when passing from a first to second stage during fixation, but for fixing without shrinkage, such stages can be omitted. The intermediate heating means for indirect heating of the thread between the drawing cylinders can also be made up of individual segments or even separate contiguous heating elements. By gradually increasing the temperature of the thread in the intermediate heating zone, sudden fluctuations of thread temperature can be avoided with less of a tendency toward thread damage.

In using the process and device of the invention on threads composed of various synthetic polymer filaments, previously unavoidable problems have been avoided so as to produce threads of much higher quality and uniformity.

As examples of treating specific threads, the following table sets forth the particular conditions used and the results achieved thereby:

TABLE EXAMPLE NO. 1 Type: Polyester Denier: 125/25 Stretch draw ratio: 1:4.55

Temperatures, degrees. Shrinkage, percent.

The invention is hereby claimed as follows:

1. In a process for the heated drawing and fixation of a thread of a filamentary synthetic thermoplastic polymer, the improvement comprising:

drawing said thread between a first heated rotatable cylinder maintained at the drawing temperature of said thread and a second heated rotatable cylinder maintained at the fixation temperature of said thread, the thread being in running contact with each of said heated cylinders, said thread thereby being heated to the drawing temperature on said first cylinder and being heated to the fixation temperature on said second cylinder; and

heating said thread over substantially the entire thread path between said cylinders in an at least partially enclosed heating zone at a temperature sufliciently high to maintain said thread at said drawing temperature but below said fixation temperature while said thread is kept free of contact with heated surfaces.

2. A process as claimed in claim 1 wherein said drawing of said thread between said cylinders and said heating step are carried out in a substantially enclosed chamber maintained under a vacuum.

3. A process as claimed in claim 2 wherein the temperature of the thread in said heating zone is gradually fixation temperature.

References Cited UNITED STATES PATENTS Hume 264-290 Spellman 28-71.3 Larkin et a1. 264-290 8 3,317,980 5/1967 Jaeggli 28-713 3,329,754 7/1967 Black 264-290 FOREIGN PATENTS 947,407 1/ 1964 Great Britain.

LOUIS K. RIMRODT, Primary Examiner US. Cl. X.R.

Kretsch 2 71 3 10 28-713; 264-235, 342, 346 

